Bee Pollination Pinnacles National Park

A Hesperapis regularis bee visits a flower of Clarkia cylindrica at Pinnacles National Park. Credit: Tania Jogesh

Study of flowers with 2 types of anthers resolves mystery that baffled Darwin.

Some flowers use a clever method to ensure reliable pollination by bees, doling out pollen gradually from two different sets of anthers.

The majority of blooming plants depend on pollinators such as bees to move pollen from the male anthers of one flower to the female preconception of another flower, making it possible for fertilization and the production of fruits and seeds. Bee pollination, nevertheless, includes a fundamental dispute of interest, due to the fact that bees are just interested in pollen as a food source.

” The bee and the plant have different objectives, so plants have progressed methods to enhance the behavior of bees to make the most of the transfer of pollen in between flowers,” explained Kathleen Kay, associate teacher of ecology and evolutionary biology at UC Santa Cruz.

Clarkia Flowers

Close-up pictures of Clarkia unguiculata and Clarkia cylindrica flowers show the 2 kinds of anthers, a noticeable inner whorl and an external whorl that mixes in with the petals. Credit: Kay et al., PRSB 2020

In a study published December 23 in Procedures of the Royal Society B, Kay’s team explained a pollination strategy including flowers with two distinct sets of anthers that vary in color, size, and position. Darwin was perplexed by such flowers, lamenting in a letter that he had actually “squandered massive effort over them, and can not yet get a glance of the significance of the parts.”

For several years, the only description presented for this phenomenon, called heteranthery, was that a person set of anthers is specialized for drawing in and feeding bees, while a less noticeable set of anthers surreptitiously dusts them with pollen for transfer to another flower. This “department of labor” hypothesis has actually been tested in different types, and although it does seem to use in a couple of cases, lots of research studies have failed to verify it.

The new research study proposes a various explanation and shows how it operates in species of wildflowers in the genus Clarkia Through a range of greenhouse and field experiments, Kay’s team showed that heteranthery in Clarkia is a method for flowers to gradually present their pollen to bees over several sees.

” What’s happening is the anthers open at various times, so the plant is administering pollen to the bees slowly,” Kay stated.

This “pollen dosing” strategy is a way of getting the bees to carry on to another flower without stopping to groom the pollen off their bodies and pack it away for shipment to their nest. Bees are highly specialized for pollen feeding, with hairs on their bodies that bring in pollen electrostatically, stiff hairs on their legs for grooming, and structures for keeping pollen on their legs or bodies.

” If a flower doses a bee with a ton of pollen, the bee is in pollen paradise and it will begin grooming and then go off to feed its offspring without checking out another flower,” Kay said. “So plants have various systems for doling out pollen gradually.
Kay’s team focused on bee pollination in two species of Clarkia, C. unguiculata(stylish clarkia) and C. cylindrica(speckled clarkia).

In these and other heterantherous clarkias, an inner whorl of anthers stands put up in the center of the flower, is aesthetically conspicuous, and matures early, launching its pollen. The external anthers then move toward the center of the flower and start to launch their pollen slowly.

” In the field, you can see flowers in various stages, and utilizing time-lapse photography we might see the entire sequence of occasions in specific flowers,” Kay stated.

Kay stated she chose to investigate heteranthery after observing clarkia flowers at a field site and recognizing that explanation didn’t fit. “I could see some flowers where one set was active, and some where the other set was active, however no flowers where both were active at the exact same time,” she said.

In C. cylindrica, the 2 sets of anthers produce pollen with various colors, which made it possible for the scientists to track where it was going. Their experiments revealed that pollen from both sets of anthers was collected for food and was likewise being moved between flowers, opposing the department of labor hypothesis.

” The color difference was practical, since otherwise it’s extremely tough to track pollen,” Kay said. “We revealed that bees are gathering and carrying pollen from both type of anthers, so they are not specialized for different functions.”

Kay stated she didn’t realize how much time Darwin had invested perplexing over heteranthery till she began studying it herself.

Reference: “Darwin’s vexing contrivance: a brand-new hypothesis for why some flowers have 2 type of anther” by Kathleen M. Kay, Tania Jogesh, Diana Tataru and Sami Akiba, 23 December 2020, Proceedings of the Royal Society B

In addition to Kay, the coauthors of the paper include postdoctoral scholar Tania Jogesh and 2 UCSC undergrads, Diana Tataru and Sami Akiba. Both trainees completed senior theses on their work and were supported by UCSC’s Norris Center for Nature.


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